Question: Simplify the following expression: $t = \dfrac{y}{8} - \dfrac{y}{5}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8$ and $5$ $\lcm(8, 5) = 40$ $ t = \dfrac{5}{5} \cdot \dfrac{y}{8} - \dfrac{8}{8} \cdot \dfrac{y}{5} $ $t = \dfrac{5y}{40} - \dfrac{8y}{40}$ $t = \dfrac{5y -8y}{40}$ $t = \dfrac{-3y}{40}$